A switch, which has a contact point that can be opened/closed by a pressing operation, includes a lock pin for maintaining a closed state of the switch. Conventionally, a cam-groove structure having a heart cam shape has been used as a cam-groove structure for sliding an end part of a lock pin.
A cam-groove structure having a heart cam shape is disclosed in, for example, Patent Literature 1. This type of cam-groove structure includes (i) a locking section for locking an end part of a lock pin and (ii) a cam groove surrounding an outer periphery of the locking section. While a closed state of a switch is maintained, the end part of the lock pin is locked by the locking section. An open/close mechanism of the switch is made possible by causing the cam groove to slide the end part of the lock pin in a fixed direction (not to slide the end part in a reverse direction).
FIG. 11 is a plan view illustrating the cam-groove structure disclosed in Patent Literature 1. According to the cam-groove structure illustrated in FIG. 11, respective depths of following three regions with respect to a lock pin in a cam groove 102 are set to be equal: (i) a free region 107, (ii) a locking region 108, and (iii) a particular flat path region in a guiding return path extending from the locking region 108 to the free region 107. According to the cam-groove structure of Patent Literature 1, an end part of the lock pin is prevented from moving in a reverse direction by (i) causing the end part of the lock pin to be in contact with a bottom surface of a cam groove by use of a pressing spring member and (ii) configuring the bottom surface of the cam groove to have a step-like form.